Fix bug when handling of multiple cookie entries with the same name (#2310)

* Fix bug when handling of multiple cookie entries with the same name

* Formatting

Author: stevejgordon

src/Elastic.Apm/Filters/RequestCookieExtractionFilter.cs

@@ -14,7 +14,7 @@ namespace Elastic.Apm.Filters
 	/// </summary>
 	internal class RequestCookieExtractionFilter
 	{
-		private static readonly WildcardMatcher[] CookieMatcher = new WildcardMatcher[] { new WildcardMatcher.VerbatimMatcher("Cookie", true) };
+		private static readonly WildcardMatcher[] CookieMatcher = [new WildcardMatcher.VerbatimMatcher("Cookie", true)];
 
 		public static IError Filter(IError error)
 		{

src/Elastic.Apm/Helpers/CookieHeaderParser.cs

@@ -42,7 +42,11 @@ public static Dictionary<string, string> ParseCookies(string cookieHeader)
 			var trimmed = cookieValue.Trim();
 			var parts = trimmed.Split('=');
 
-			if (parts.Length == 2 && !string.IsNullOrEmpty(parts[0]) && !string.IsNullOrEmpty(parts[1]))
+			// Fow now, we store only the first value for a given key. This aligns to our nodeJS agent behavior.
+			if (parts.Length == 2 
+				&& !string.IsNullOrEmpty(parts[0]) 
+				&& !cookies.ContainsKey(parts[0])
+				&& !string.IsNullOrEmpty(parts[1]))
 			{
 				cookies.Add(parts[0], parts[1]);
 			}
@@ -75,8 +79,14 @@ public static Dictionary<string, string> ParseCookies(string cookieHeader)
 				var keyString = key.ToString();
 				var valueString = value.ToString();
 
-				if (!string.IsNullOrEmpty(keyString) && !string.IsNullOrEmpty(valueString))
+				// Fow now, we store only the first value for a given key. This aligns to our nodeJS agent behavior.
+#if NETSTANDARD2_0
+				if (!string.IsNullOrEmpty(keyString) && !cookies.ContainsKey(keyString) && !string.IsNullOrEmpty(valueString))
 					cookies.Add(keyString, valueString);
+#else
+				if (!string.IsNullOrEmpty(keyString) && !string.IsNullOrEmpty(valueString))
+					cookies.TryAdd(keyString, valueString);
+#endif
 			}
 
 			span = span.Slice(foundComma ? separatorIndex + 1 : span.Length);

test/Elastic.Apm.Tests/HelpersTests/CookieHeaderParserTests.cs

@@ -26,31 +26,36 @@ public void ParsesHeadersCorrectly(string input, Dictionary<string, string> expe
 		result.Should().Contain(expected);
 	}
 
-	public static IEnumerable<object[]> TestData() => new[] {
-		new object[] { null, null },
-		new object[] { "", null },
-		new object[] { "Key1=Value1", new Dictionary<string, string>() { { "Key1", "Value1" }} },
-		new object[] { "Key1=Value1,Key2=Value2", new Dictionary<string, string>()
+	public static IEnumerable<object[]> TestData() => [
+		[null, null],
+		["", null],
+		["Key1=Value1", new Dictionary<string, string>() { { "Key1", "Value1" }}],
+		[ "Key1=Value1,Key2=Value2", new Dictionary<string, string>()
 		{
 			{ "Key1", "Value1" },
 			{ "Key2", "Value2" }
-		}},
-		new object[] { "Key1=Value1,Key2=Value2,Key3=Value3", new Dictionary<string, string>()
+		}],
+		[ "Key1=Value1,Key2=Value2,Key3=Value3", new Dictionary<string, string>()
 		{
 			{ "Key1", "Value1" },
 			{ "Key2", "Value2" },
 			{ "Key3", "Value3" }
-		}},
-		new object[] { "Key1=Value1; Key2=Value2", new Dictionary<string, string>()
+		}],
+		[ "Key1=Value1; Key2=Value2", new Dictionary<string, string>()
 		{
 			{ "Key1", "Value1" },
 			{ "Key2", "Value2" }
-		}},
-		new object[] { "Key1=Value1; Key2=Value2; Key3=Value3", new Dictionary<string, string>()
+		}],
+		[ "Key1=Value1; Key2=Value2; Key3=Value3", new Dictionary<string, string>()
 		{
 			{ "Key1", "Value1" },
 			{ "Key2", "Value2" },
 			{ "Key3", "Value3" }
-		}}
-	};
+		}],
+		[ "Key1=Value1; Key2=Value2; Key1=Value3", new Dictionary<string, string>()
+		{
+			{ "Key1", "Value1" },
+			{ "Key2", "Value2" }
+		}],
+	];
 }